Orthodontic treatment of improperly positioned teeth involves the application of mechanical forces to urge the teeth into correct alignment. The most common form of treatment involves use of orthodontic brackets which are small slotted bodies configured for direct cemented attachment to the labial or lingual surfaces of the teeth, or alternatively for attachment to metal bands which are in turn cemented or otherwise secured around the teeth.
A resilient curved archwire is then seated in the bracket slots, and the archwire is bent or twisted before installation whereby the restoring force exerted by the seated resilient wire tends to shift the teeth into orthodontically correct alignment. Depending on the shape of the archwire (both round and rectangular cross sections are in common use) and the orientation of the bracket slot, it is possible to apply forces which will shift, rotate or tip the teeth in any desired direction.
Conventional orthodontic brackets include tie wings around which small ligature wires are tied to hold the archwire in a securely seated position in the brackets. Ligatures or some other form of fastening means are essential to insure that the activated archwire is properly positioned around the dental arch, and to prevent the wire from being dislodged from the bracket slots during chewing of food, brushing of the teeth, or application of other forces to the wire by the patient.
Orthodontists are skilled in the manipulation of ligatures, but the placement of these small wires nevertheless requires considerable time during initial installation of an archwire. It is also normally necessary to remove and replace the ligatures at one or more intermediate stages of orthodontic treatment involving sequential use of several different kinds of archwires, leading to further essentially unproductive chair time for the orthodontist and possible discomfort for the patient.
Ligatures also tend to make proper oral hygiene more difficult as the wires can trap food particles, and the twisted ends of a ligature may be shifted during chewing into a position where irritation of the patient's gums or cheek tissue occurs. Broken or dislodged ligatures may also require emergency patient visits to the orthodontist, and broken ligatures further present the hazard that a loose piece of wire may be swallowed or inhaled into the patient's breathing passages.
Many of the problems presented by ligatures are overcome by self-locking orthodontic brackets which in many cases eliminate need for these tie wires. One approach to a self-locking design involves use of a rotatable locking member which is coupled to the bracket, and is movable to open and close the bracket slot, the archwire being held captive in the slot when the locking member is in the closed position. Bracket configurations of this type are disclosed in my U.S. Pat. Nos. 4,077,126, 4,371,337, 4,419,078 and 4,559,012.
The present invention is directed to a different style of self-locking bracket using a sliding member which is linearly movable in an occlusogingival direction to open and close the bracket archwire slot. This new design has a desirably low profile when mounted on a tooth, and features a detent retention in both the open and closed positions, and with greatly increased resistance to complete removal of the slide member from the bracket body.
The new bracket eliminates any need for time-consuming archwire ligation in a high percentage of cases, and lock-pin sockets are provided to enable ligation in an occasional situation where the archwire cannot be initially seated due to a badly malpositioned tooth. The bracket is smoothly contoured to minimize food-trapping recesses, and is useful in both light-wire and edgewise techniques without restriction on archwire cross section. The bracket is also useful in straight-archwire techniques where desired force vectors (e.g., torque, tip and rotation) are designed into the bracket.